The invention relates to a thermostatic valve for a cooling system of an internal combustion engine, in particular of an internal combustion engine of a motor vehicle.
A cooling system for an internal combustion engine usually comprises a coolant circuit 10 in which the present invention can also be used and which is schematically illustrated in FIG. 1.
The coolant, for example water, is fed to the internal combustion engine 12 via a coolant feed line 14 by means of a pump 16. After the coolant has passed through the internal combustion engine 12 and correspondingly has been heated up owing to an exchange of heat, it flows via a coolant discharge line 18, a coolant return line 20 and a coolant radiator line 22 to a radiator 24 in order to be cooled again in said radiator by means of an exchange of heat with cooling air. The coolant which is cooled in this way is then fed back from the radiator 24 to the internal combustion engine 12 via the feed line 14.
If the temperature of the coolant flowing out of the internal combustion engine 12, which is sensed by a suitable temperature sensor 26 in the discharge line 18, for example during the warm-up phase of the internal combustion engine, is relatively low after startup of the internal combustion engine and it is not necessary to cool the coolant, the coolant is fed back directly to the feed line 14 via a coolant bypass line 28 without running through the radiator 24. The coolant thus arrives back at the internal combustion engine 12 without being cooled so that it is successively heated until it reaches a temperature which requires cooling. The coolant is therefore then directed through the radiator 24.
Usually a thermostatic valve 30 is provided for directing the coolant from the return line 20 into the radiator line 22 and/or the bypass line 28. The thermostatic valve 30 controls the opening and closing of a first passage from an inlet connection 32 which is connected to the return line 20, to a first outlet connection 34a which is connected to the radiator line 22, and of a second passage from the inlet connection 32 to a second outlet connection 34b which is connected to the bypass line 28. The control is carried out as a function of the temperature of the coolant sensed at the outlet of the internal combustion engine 12 by the temperature sensor 26.
Furthermore, the coolant which is heated in the internal combustion engine 12 can also be used to heat a passenger compartment of a motor vehicle. For this purpose, the coolant circuit 10 has a coolant heater line 36 which branches off from the discharge line 18 and by means of which the coolant is carried to a heat exchanger 40 by means of a pump 38. In the heat exchanger 40, the warm coolant exchanges heat with an air stream which is blown into the passenger compartment. The coolant is cooled as a result of heat being transferred to the air stream of the heating system of the passenger compartment. The coolant which is cooled in this way is then fed back to the feed line 14.
In order to heat the passenger compartment when the internal combustion engine 12 is stationary, an additional heater (referred to as a stationary-vehicle heater, not illustrated) may optionally be provided, said heater being connected to the heat exchanger 40 in parallel with the coolant circuit 10.
For example, what is referred to as a rotary slide thermostatic valve, whose method of operation and switched states are illustrated schematically in FIGS. 2A to 2D is known from the prior art as a thermostatic valve 30 for regulating the temperature of the coolant which is fed to the internal combustion engine 12.
As illustrated in the Figures, the rotary slide thermostatic valve 30 has a valve chamber 42 which has the inlet connection 32 in the axial direction and the first and second outer connections 34a, 34b in the radial direction. A rotary slide 44 which can rotate about the axis which is perpendicular to the plane of the drawing is provided in the chamber 42, said rotary slide 44 being constructed with two closure areas and two opening areas in such a way that the switched states described below can be set.
In the first switched state of the thermostatic valve 30, which is illustrated in FIG. 2A, for the purpose of what is referred to as full throttle, the rotary slide 44 is placed in such a rotary position that both the first and second outlet connections 34a, 34b are closed. As a result, the coolant is prevented from circulating and the coolant is stationary, inter alia also in the internal combustion engine 12, where it consequently heats up. The warming-up of the internal combustion engine 12 can be promoted by this full throttle.
In the warm-up operating mode of the internal combustion engine 12, the second outlet connection 34b is cleared by the rotary slide 44, while the first outlet connection 34a remains closed, as illustrated in FIG. 2B. In this way, the coolant is returned to the internal combustion engine 12 only via the bypass line 28 so that it gradually heats up.
As the temperature of the coolant rises, partial cooling of the coolant becomes necessary so that the thermostatic valve 30 is switched into the mixed operating mode. In this mixed operating mode, the rotary slide 44 is in such a rotary position that both outlet connections 34a and 34b are opened (see FIG. 2C) so that part of the coolant flows through the radiator 24 and the other part is fed back directly to the internal combustion engine 12.
When there is a maximum demand for cooling capacity, the first outlet connection 34a is fully opened and the second outlet connection 34b is closed (cooling operating mode according to FIG. 2D) so that all of the coolant is directed through the radiator 24 for the purpose of cooling.
The operating positions of the rotary slide thermostatic valve 30 can be set quickly and precisely by means of a suitable electromechanical control system, and the rotary position of the rotary slide 44 can also be sensed electronically. The high costs of such a rotary slide thermostatic valve, in particular for controlling it, as well as its heavy weight and its large size are disadvantageous.
An object of the present invention is to provide a thermostatic valve for a cooling system of an internal combustion engine, with which the switched states of a rotary slide thermostatic valve can be set and the switching times are as short as possible. Furthermore, the thermostatic valve should be as small as possible and as lightweight as possible and it should also be inexpensive.